Auxiliary hoist control



March 20, 1962 c. w. MERRILL ET AL 3,025,702

AUXILIARY HOIST CONTROL Filed March 10, 1959 4 Sheets-Sheet l INVENTOR.

March 20, 1962 c. w. MERRILL ET AL 3,025,702

AUXILIARY HOIST CONTROL 4 Sheets-Sheet 2 Filed March 10, 1959 March 20, 1962 c. w. MERRILL ET AL AUXILIARY HOIST CONTROL 4 Sheets-Sheet 5 Filed March 10, 1959 v H v R J: m m 5% m M m V n W a LG E J March 1962 c. w. MERRILL ET AL AUXILIARY HOIST CONTROL 4 Sheets-Sheet 4 lg hQ INVENTORJ 69m; W /%mu ttes This invention relates to auxiliary hoist controls. More particularly, the invention relates to an auxiliary hoist control which may be utilized to raise and lower heavy objects over short distances and can accurately position the objects with respect to the vertical. In addition, the invention may be utilized as a tension measuring device.

Auxiliary hoist controls have been previously used in connection with hoists, such as a block and tackle, for the assemblage of heavy structures. An example of such a hoist control is illustrated in U.S. Patent No. 2,500,459, issued March 14, 1950, to W. S. Hoover et al., and assigned to the assignee of the present application. In such devices provision has been made for the control of hydraulic fluid in a piston cylinder arrangement connected to a load engaging means, whereby the load supported from the load engaging means is lowered through the by-passing of the hydraulic fluid around the piston. Such devices have heretofore failed to gain widespread acceptance as auxiliary control devices.

The improved auxiliary hoist control of the present invention provides positive control over the lowering and raising of extremely heavy loads supported by the control. Such control has not been available in the devices known heretofore.

Loads in excess of twenty tons may be accurately positioned according to the present invention. According to the present invention, a valve assembly provides for the controlled escape of that portion of the hydraulic fluid which supports the piston within the cylinder. The hydraulic fluid escapes through the valve assembly into an annular storage chamber. The storage chamber is divided into two portions by a separator ring. The lower portion of the storage chamber contains the escaped hydraulic fluid. The upper portion of the storage chamber is sealed from both the hydraulic fluid and the external atmosphere. Air or other compressible fluids are contained in the upper storage chamber. As the hydraulic fluid escapes from the cylinder into the lower storage chamber, the separator ring is forced upward so as to compress the fluid stored in the upper storage chamber. This compression of the fluid in the upper storage chamber provides a method of retaining the balance of pres-- sures throughout the system and for returning the piston to its original, retracted position.

The valve assembly is of novel construction and also functions to permit the passage of hydraulic fluid so as to equalize the pressures within the cylinder and in the annular storage area when the load is removed. In other words, when the load is removed, the valve assembly, which previously acted to allow passage of fluid from the cylinder to the annular storage area, now functions automatically as a dump valve to allow passage of fluid from the annular storage area to the cylinder. This valve assembly is hereinafter referred to as the down valve.

A pump is provided in the present invention to furnish means for returning the piston to its retracted position when a load is engaged. The pump withdraws hydraulic fluid from the storage chamber and injects the fluid into the cylinder, thereby forcing the piston upward. This pump is hereinafter referred to as the up pump.

The auxiliary hoist control in general and the down valve and up pump in particular are of special novel conice struction which may be better understood by reference to the drawing in which:

FIGURE 1 is a front elevation of the auxiliary hoist control;

FIGURE 2 is a front elevation in section of the auxiliary hoist control;

FIGURE 3 is a sectional view taken along lines 33 of FIG. 1 with the down valve assembly and up pump assembly removed;

FIGURE 4 is a fragmentary elevation taken along lines 44 of FIG. 1, partially in section;

FIGURE 5 is a sectional viewof the up pump of the auxiliary hoist control;

FIGURE 6 is a sectional view of the down valve of the auxiliary hoist control;

FIGURE 7 is an enlarged partial sectional view of the down valve and piston, illustrated in FIG. 6, and

FIGURE 8 is a further enlarged partial sectional view of the down valve and piston illustrated inFIG, 6.

Referring to FIG. 1, there is shown an auxiliary hoist control 11 which consists principally of a body portion 12, an upper head 13, to which a top eye 14 is connected, and a lower head 15. A rotatable socket having a lower eye 17 is connected to a shaft extending through the lower head 15. The lower head 15 has a down valve assembly 18 and an up pump assembly 19 extending therethrough. A hydraulic fluid pressure gauge 21 and a compressible fluid pressure gauge 22 are located on the body portion 12 of the auxiliary hoist control. A compressible fluid filler plug 25 closes a compressible fluid addition inlet (see FIG. 2). A breather cap 26 vents the space above the piston to the atmosphere through a passage 27 (see FIG. 2) in the upper head.

FIGURE 2 shows a sectional elevation of the auxiliary hoist control 11 of FIG. 1. A piston 30 is connected to a piston rod 31, the lower end of which is attached to the lower eye 17. The piston is inserted in a cylinder 32 having a wall 33. Concentric about the cylinder 32 there is positioned a second cylinder 34 so as to form a concentric annular volume with respect to the cylinder 32. This annulus has a lower portion 35 which is divided by a solid brass separator ring 36 from an upper portion 37. The lower portion 35 is used as, and hereinafter referred to as, the hydraulic fluid storage area. The upper portion 37 is used as, and hereinafter referred to as, the compressible fluid storage area. The separator ring 36 has an inner O-ring 3S and outer O-ring 39 which assist in forming a seal between the two storage areas.

A down valve assembly bore 40 and an up pump assembly bore 41 are located in the lower head assembly 15.

FIGURE 3 is a sectional view of the lower head 15. Two bores 40 and 41 contain the down valve assembly 18 and the up pump assembly 19 respectively, which assemblies are not shown in FIG. 3 for purposes of clarity. Partial sections of these assemblies are shown in FIGS. 5, 6. A down valve assembly inlet hole 55 and outlet hole 56 provide apertures for by-passing hydraulic fluid from the cylinder into the hydraulic fluid storage area by means of the down valve assembly. Up pump inlet and outlet holes 59 and 60 provide apertures for withdrawing hydraulic fluid from the storage area and injecting the fluid into the cylinder in conjunction with the up pump assembly 19. A gauge passage 61 connects the cylinder to the hydraulic fluid pressure gauge 21. A hydraulic fluid addition passage 62 is closed by a cap 63.

Hydraulic fiuidis contained in the inner cylinder 32. When a tensioning load is applied between the top eye 14 and the lower eye 17, the hydraulic pressure exerted by the hydraulic fluid in the inner cylinder 32 increases. Through the action of the down valve assembly, as will subsequently be described, this hydraulic fluid is selec tively passed from the inner cylinder 32 into the hydraulic fluid storage area 35. A decrease in the volume of hydraulic fluid contained in the inner cylinder 32 due to the movement of the piston 30 in response to the tensioning load, will result in the movement of the piston rod 31 out of the lower head assembly 15 in proportion to the amount of hydraulic fluid passed into the hydraulic fluid storage area 35.

An increase in the volume of hydraulic fluid stored in the hydraulic fluid storage area 35 will move the separator ring 36 in a direction toward the upper head 13. Air or other compressible fluid is normally stored in the cornpressible fluid storage area 37. The movement upward of the separator ring 36 will compress the fluid stored in the compressible fluid storage area 37 in proportion to the amount of movement of the separator ring 36 which occurs, and therefore in proportion to the amount of hydraulic fluid transferred from the cylinder 32 to the hydraulic fluid storage area 35.

The auxiliary hoist control 11 is so constructed that there is an appreciable difference between the cross sectional area of the storage areas 35 and 37 and the cross sectional area of the cylinder 32. The proportioning of these cross sectional areas permits the ultimate capacity of the unit to be widely varied so long as the structural limitations of the unit are not exceeded.

For example, assuming that there is a 1:2 ratio between the storage cross section and the cylinder cross section areas, the force which the compressible fluid will be required to exert on the separator ring, and consequently, on the hydraulic fluid, in order to exactly counterbalance a 20,000 pound tensioning force applied across the auxiliary hoist 11 will be only 10,000 pounds. If the cross section area of the cylinder 32 is 50 square inches, when the compressible fluid has been compressed to a pressure of 400 pounds per square inch, the system will be in equilibrium.

Assuming that the piston and piston rod are in their fully retracted position, the position shown in FIG. 2, and the compressible fluid in the upper annular area is at atmospheric pressure, when the piston is subsequently moved toward the lower head 15 by a tensioning force of 20,000 pounds, the system will be in equilibrium when the compressible fluid is compressed to approximately one twentyfifth of its original volume.

However, if the pressure existing in the compressible fluid area is appreciably greater than ambient pressure when the piston 30 and piston rod 31 are in their fully retracted position, the application of a tensioning load of 20,000 pounds will cause the required 10,000 pounds pressure to be exerted by the compressible fluid upon the separator ring prior to the piston travel required for equilibrium in the preceding case. Thus, by prepressuring the upper annular storage area, it is possible to limit the ultimate extension of the auxiliary hoist in accordance both with the tension load applied and with the prepressuring used.

Prepressuring of the compressible fluid storage area may be accomplished through a compressible fluid inlet 45 (FIG. 2). By means of this prepressuring facility, the auxiliary hoist control may be also utilized as a tension measuring device. Thus, knowing the pressure initially existing in the compressible fluid area, the tension exerted may be measured by the amount of extension of the piston rod.

FIGURE 4 is an elevation, partially in section, showing the upper head 13. A compressible fluid gauge outlet passage65 connects the compressible fluid gauge 22 to the upper annular storage area.

FIGURE 5 is a sectional view of the up pump assembly 19. The up pump assembly consists of a hollow body portion 80 to which isconnected an extension body 81 at one end and a piston 82 at the other. A pump handle 83 having a knob 84 extends into the body of the piston- 82 and is held in position by a set screw .85. A handle bearing 86 holds the handle 83 generally in position in the up pump body and reduces friction due to handle movement. The up pump body 80 has a canted slot 87 indicated by the dotted line along which the handle 83 may be moved. A torsion spring 88 is connected between the piston and the pump body to rotatably return the piston to the position shown after it has been moved along the canted slot. Adjacent one end of the torsion spring 88 are a pair of flanges 89 which contain an O-ring 90. The hollow pump body 80 narrows adjacent the flanges 89 so that the flanges 89 and the O-ring 90 provide a seal. The hollow pump body 80 has a pair of hydraulic fluid inlets 91 extending therethrough. The portion of the piston 82 adjacent the hydraulic fluid inlets 91 is of smaller diameter than the inner diameter of the pump body 80 at that point, thereby providing an annular hydraulic fluid containing space 92. A second concentric hydraulic fluid containing space 92a obviates the necessity for aligning the inlets 91 with the inlet 59 (see FIG. 3) of the lower head.

In the annular hydraulic fluid containing space 92, the piston has a pair of hydraulic fluid inlet passages 93 which open into a longitudinal storage passage 94 within the piston 82 so as to form a small hydraulic fluid storage space. The longitudinal passage 94 opens onto a larger diameter ball check valve passage 95. In the ball section valve passage 95 there is contained a ball 96 held in position by means of a ball check spring 97 so as to close the longitudinal storage passage 94. The ball check spring 97 is held in compression by means of a washer 98 positioned against a snap ring 99 which engages the outer surface of the ball check valve passage 95.

The extension body 81 has a hollow cylindrical central portion 100 and contains a ball 101 which is held against a check valve seat 102 in the form of a ring by a check valve spring 103. The ball 101 and check valve spring 103 are contained within the hollow central body portion 100 of the body extension 81 when the up pump 19 is assembled. Two hydraulic fluid outlet holes 105 extend from the outer surface of the extension body 81 into the hollow central portion 100. A first O-ring 106, in cooperation with the cylindrical bore 41 of the lower head and a shoulder on the pump body 80, seals the hydraulic fluid contained in the annular storage area in one direction. A second O-ring 107 provides a hydraulic fluid seal between the inlet holes 91 and the outlet holes 105. A third O-ring 108 provides a seal for the hydraulic fluid contained adjacentthe extension body 81.

An O-ring 109 seals the surface between the piston and body next to the inlet holes 93 in the direction of the extension body 81. An O-ring 110 seals the junction of the check valve 102, the extension body 81, and the pump body 80.

The up pump is operated by rotating the up pump handle 83. Due to the canted construction of the slot 87' which contains the handle 83, the piston 82 is driven toward the extension body 81 when the pump handle 83 is so rotated. Hydraulic fluid from the annular storage cylinder fills the inlet holes 91 and annular volume 92 associated therewith, together with the check valve inlet holes 93 and longitudinal storage passage 94. The hollow volume extending between the first ball 96 and the second ball 101 is filled with hydraulic fluid. The movement of the piston 82 towards the extension body 81 compresses this latter volume of hydraulic fluid to a pressure which exceeds the pressure existing in the cylinder 32.

. When the pressure exerted on this compressed volume between the check balls 96 and 101 exceeds the combined pressure existing in the cylinder 32 and the pressure exerted on the ball 101 by the check valve spring 103, the ball 101 moves against the check valve spring 103 to the extent required to compress the spring 103 to equalize for the excess in pressure existing in the fluid between the trapped check balls. However, the movement of the check ball 101 against the check ball spring 103 moves the check ball 101 away from the check valve seat 102 which the check ball 101 formerly sealed. Thereupon, the fluid trapped between the two check balls escapes through the outlet holes 105 into the annular volume existing between the up pump assembly and the cylindrical bore 41 of the lower head and then into the cylinder 32 through the up pump outlet hole 60 (see FIG. 3). Hydraulic fluid will continue to so flow until the pressure existing in the fluid between the two check balls and the pressure existing in the cylinder is equalized. T hereupon, the ball 101 will be forced against the check valve seat 102 by the check valve spring 103, again sealing hydraulic fluid between the two check balls.

Release of the pump handle 83 allows the torsion spring 38 to return the pump handle 83 to its normal position and retract the piston 82 from the advanced position resulting from the prior rotating movement of the pump handle. Retractio-n of the piston 82 reduces the pressure on the fluid trapped between the two check balls. Check ball 101 remains seated against the check valve seat 102 due to the pressure exerted by the fluid in the hollow central portion 100 of the extension body 81 against the ball 101. The ball 96 which heretofore closed the longitudinal passage 94 by the action of the compressed fluid trapped between the two check balls and also by the action of the check valve spring 95, is now moved away from the valve seat by the pressure exerted on the ball 96 by the fluid contained in the holes 91 and 93 and the longitudinal passage 94. When the hydraulic fluid contained between the two check balls 96 and 101 is at a pressure equal to that of the hydraulic fluid storage area 35, the ball 96 is moved by the check valve spring 97 to close the longitudinal passage 94.

Thus, fluid is extracted from the annular storage area and passed through the holes 91, 93 and the passage 94 around the check ball 96 and into the volume contained between the check balls 96 and 101. A subsequent movement of the pump handle, as previously described, will thereupon result in the repetition of the pumping cycle which was described above.

FIGURE 6 is a sectional view of the down valve assembly 13. The down valve assembly 18 consists of a body 120 and a body extension 121 which together contain the various parts of the valve. A down valve handle 123 having a knob 124 is inserted through the body 120 into the hollow central portion thereof. A valve actuator 125 is contained in the hollow central portion 122 of the body 120 and engages the handle 123. The handle 123 is held against the valve actuator 125 by means of a set screw 126. A torsion spring 127 is contained within the hollow cylindrical portion of the body 120 and is operable to return the valve handle 123 to the position shown when it has been rotated. A canted slot illustrated by the dotted line 128 allows the valve handle 123 to be rotated. A handle bearing 86 holds the handle 123 generally in position in the down valve assembly 120 and reduces friction due to handle movement. Rotation of the valve handle causes the actuator 125 to move toward the body extension 121. The actuator has a stern portion 129 extending through the hollow central portion 122. A pair of outlet holes 130 extend through the body portion 120 and open into the hollow cylindrical central section 122. A seal of the hollow cylindrical central portion 122 in the direction of the valve handle 123 is formed by a pair of flanges 131 and an O-ring 132.

A valve seat 133 is located at the junction of the body 120 and the extension 121. A check valve piston 134 is contained within the check valve seat 133. The check valve piston 134 is of novel construction and illustrated in greater detail in FIG. 7. An O-ring 135 seals the junction between the body section 120, the extension section 121 and the valve seat 133.

The annular chamber formed by the hollow cylindrical central portion 122 and the stem 129 has dimensions such that its longitudinal cross section area is at least three times greater than its lateral cross sectional area with the valve handle in the position shown. The use of this chamber configuration provides proper location of the inlet and outlet holes for the valve. A helper spring 136 located in the extension 121 holds the valve piston 134 against the valve seat 133. An O-ring 138 seals the outlet holes in the direction of the valve handle. An O-ring 139 seals the outlet holes in the opposite direction. A pair of inlet holes 140 open into a hollow central portlon 141 or the extension 121 between the helper spring 136 and the valve seat 133. An O-ring 142 provides a seal adjacent the inlet holes 140.

FIGURE 7 shows in detail the construction of the valve piston 134 and valve seat 133. The valve piston 134 consists of a piston head 145 which is connected to the main body portion 146 by a shoulder 147. A stem 148 extends from the main body portion 146 in the opposite direction from the piston portion 145. The piston head 145 has a slight narrowing taper in the direction away from the main body portion 146.

It should be noted that the valve piston consists of an integral unit contained within the valve seat 133. The valve seat 133 has an annular portion 149 extending down the main body portion 146. The main body portion 146 preferably is constructed of square stock having slightly rounded edges. With such a construction, the extended annular portion 149 of the valve seat 133 surrounding the body portion 146 serves to align the head portion 145 and shoulder portion 147 with the orifice of the valve seat 133, while the stern projecting from the body portion 146 in the opposite direction from the head portion 145 serves to provide firm contact with the helper spring 136 contained in the extension 1211.

Referring to FIG. 6, the operation of the down valve assembly will now be described. The down valve handle is rotated along the canted slot 128, driving the actuator 125 in the direction of the extension 121. The stem of the actuator is in contact with the face of the valve piston head portion 145. Prior to movement of the down valve handle 123, the valve seat 133 and the valve piston shoulder 147 form a seal to prevent movement of fluid from the inlet holes 140 through the valve assembly toward outlet holes 130. The movement of the piston 134 caused by the actuator stem 129 driving the piston stem 148 against the helper spring 136 opens the seal formed between the shoulder 147 and the valve seat 133. However, the piston head 145 is contained within the orifice of the valve seat 133. A small annular by-pass area between the piston head portion 145 and the valve seat 133 exists. This small annular volume allows the movement of hydraulic fluid from the inlet holes 140 to the outlet holes 130. As the rotation of the valve handle 123 continues, the piston head portion 145 is moved further back within the valve seat orifice. After the portion of the valve head portion 145 adjacent the shoulder 147 passes completely through the orifice, further movement of the valve head portion in this direction will result in an increase in the annular cross section available for the passage of hydraulic fluid, due to the taper of the valve head portion 145. Therefore, the rate of passage of fluid through the down valve assembly is proportional to the amount of rotation of the down valve handle after the constant rate displacement of the piston head has been exceeded.

When the pressures existing between the hydraulic fluid in the cylinder and the hydraulic fluid in the annular storage chamber are equal, no flow of fluid through the down valve assembly will occur. If the valve handle 123 is thereupon returned to the position shown in FIG. 6, the helper spring 136 will force the piston shoulder 147 against the valve seat 133, thereby again sealing the annular storage chamber against a further introduction of fluid from the hydraulic fluid of the cylinder.

As was previously stated, the upper portion of the annular storage chamber contains a compressible fluid in a confined volume. When the tension causing the extension 'of the auxiliary hoist is removed, thereby releasing 'the pressure on the hydraulic fluid in the cylinder, the compressed fluid in the compressible fluid storage area 37 exerts a pressure on the hydraulic fluid in the hydraulic fluid storage area 35 which is greater than the pressure existing on the hydraulic fluid in the cylinder 32. The down valve assembly 18 thereupon commences to function as a dump valve due to its unique construction. The hydraulic fluid under high pressure in the hydraulic fluid storage area 35 forces the piston head 145 to retract through the valve seat 133 orifice. Hydraulic fluid flows from the hydraulic fluid storage area 35, through the outlet holes 130, the valve seat 133 orifice, the inlet holes 140 and into the cylinder 32. This flow of fluid continues until the piston and rod have been completely retracted or until the pressures exerted upon the separator ring by the compressible fluid and by the hydraulic fluid are equalized.

We claim:

1. An auxiliary hoist control and tension measuring device comprising a first cylinder, a piston contained within the first cylinder, a second cylinder of greater diameter than the first cylinder positioned about the first cylinder to form an annulus therebetween, an upper head closing the upper ends of the first and second cylinders and having an atmospheric vent extending therethrough to the first cylinder and a pressure sealed inlet extending therethrough to the annulus, an eye attached to the upper head, a lower head closing the lower ends of the first and second cylinders and having firstand second parallel cylindrical bores extending laterally therethrough perpendicular to the cylinders, with passages connecting each bore with the first cylinder and each bore with the annulus, a piston rod connected to the piston and extending through the lower head to connect with a lower eye, a solid brass separator ring mounted in the annulus so as to divide the annulus into two portions, a hydraulic fluid contained in the cylinder between the piston and the lower head, a hydraulic fluid contained in the annulus between the separator ring and the lower head, a compressible fluid contained in the annulus between the separator ring and the upper head, a down valve assembly, positioned in the first lower head bore, said assembly having an inlet positioned to allow passage of hydrauiic fluid from the cylinder into the valve and an outlet positioned to allow passage of hydraulic fluid from the valve into the annulus through the passages connecting the first bore to the cylinder and the annulus, and a valve including as a first integral unit a valve seat having an orifice and an extended tubular aligning section positioned between the orifice and the first bore inlet and as a second integral unit a valve piston consisting of a frusto-conical piston head positioned in said orifice and opening onto a shoulder of a substantially rectangular valve body contained within the tubular aligning section, the rectangular valve body terminating in a cylindrical stern located adjacent the first bore inlet, a helper spring compressively held against said cylindrical stem so as to urge the shoulder against the inlet side of the orifice to form a seal when the hydraulic pressure in the annulus does not exceed the hydraulic pressure in the cylinder, and valve actuating means, in which the down valve actuating means is selectively operable to displace the piston head longitudinally in the direction of the down valve inlet to permit passage of hydraulic fluid through the annular volume thereby formed between the orifice and the piston head, an up pump assembly in the second bore and comprising an inlet allowing passage of hydraulic fluid from the annulus to a first ball check valve through the passage connecting the second bore to the annulus and an outlet allowing passage of hydraulic fluid from a second ball check valve into the cylinder through the passage connecting the second bore to the cylinder, in which the two ball check valves are spring loaded to urge the balls toward the inlet so as to close the valves and form a hydraulic fluid storage space between the valves, and pump actuator means for selectively moving'the first ball check valve toward the second bore to compress the hydraulic fluid stored between the two balls, whereby the second ball check valve opens and a portion of the compressed hydraulic fluid flows into the cylinder, said actuator means thereupon being operable to return under the first ball check valve to its original position, whereby the first ball check valve opens and hydraulic fluid is extracted from the annulus into the hydraulic fluid storage space between the two valves, a first pressure gauge operable to indicate the pressure of the hydraulic fluid in the cylinder, and a second pressure gauge operable to indicate the pressure of the compressible fluid in the annulus.

2. An auxiliary hoist control comprising a first cylinder, a piston contained within the first cylinder, a second cylinder of greater diameter than the first cylinder positioned about the first cylinder to form an annulus therebetween, an upper head closing the upper ends of the first and second cylinders and having an atmospheric vent extending therethrough to the first cylinder and a pressure sealed inlet extending therethrough to the annulus, first attaching means connected to the upper head, a lower head closing the lower ends of the first and second cylinders and having first and second parallel cylindrical bores extending laterally therethrough perpendicular to the cylinders, at least one fluid passage connecting each bore with the first cylinder and each bore with the annulus, a piston rod connected to the piston and extending through the lower head, second attaching means connected to the piston rod remote from the piston, an integral metallic separator ring mounted in the annulus so as to divide the annulus into a hydraulic fluid portion between the separator ring and the lower head and a compressible fluid portion between the separator ring and the upper head, a down valve assembly positioned in the first lower head bore, said assembly having an inlet positioned to allow passage of hydraulic fluid from the cylinder into the valve and an outlet positioned to allow passage of hydraulic fluid from the valve into the annulus through the passages connecting the first bore to the cylinder and the annulus, and a valve including as a first integral unit a valve seat having an orifice and an extended tubular aligning section positioned between the orifice and the first bore inlet and as a second integral unit a valve piston consisting of a frusto-conical piston head positioned in said orifice and opening onto a shoulder of a substantially rectangular valve body contained within the tubular aligning section, the rectangular valve body terminating in a cylindrical stern located adjacent the first bore inlet, a helper spring compressively held against said cylindrical stern so as to urge the shoulder against the inlet side of the orifice to form a seal when the hydraulic pressure in the annulus does not exceed the hydraulic pressure in the cylinder, and a valve actuating means, in which the down valve actuating means is selectively operable to displace the piston head longitudinally in the direction of the down valve inlet to permit passage of hydraulic fluid through the annular volume thereby formed between the orifice and the piston head and an up pump assembly in the second bore and comprising an inlet allowing passage of hydraulic fluid from the annulus to a first ball check valve through the passage connecting the second bore to the annulus and an outlet allowing passage of hydraulic fluid from a second ball check valve into the cylinder through the passage connecting the second bore to the cylinder, in which the two ball check valves are spring loaded to urge the balls toward the inlet so as to close the valves and form a hydraulic fluid storage space between the valves, and pump actuator means for selectively moving the first ball check valve toward the second bore to compress the hydraulic fluid stored between the two balls, whereby the second ball check valve opens and a portion of the compressed hydraulic fluid flows into the cylinder, said actuator means thereupon being operable to return under the first ball check valve to its original position, whereby the first ball check valve opens and hydraulic fluid is extracted from the annulus into the hydraulic fluid storage space between the two valves.

3. A valve assembly comprising a hollow body portion having an inlet positioned to allow passage of hydraulic fluid thereinto and an outlet positioned to allow passage of hydraulic fluid therefrom, a valve portion having, as a first integral unit, a valve seat with an orifice extending therethrough and an extended tubular aligning section positioned between the orifice and the inlet and, as a second integral unit, a valve piston consisting of a frusto-conical piston head positioned in said orifice and opening onto a shoulder of a substantially rectangular valve piston body contained Within the tubular aligning section, the rectangular valve piston body terminating in a cylindrical stem located adjacent the inlet, and a helper spring compressively held against said cylindrical stern by the body portion so as to urge the shoulder against the inlet side of the orifice so as normally to form a seal, and valve actuating means selectively operable to displace the piston head longitudinally in the direction of the inlet to permit passage of hydraulic fluid through the annular volume thereby formed between the orifice and the piston head.

References Cited in the file of this patent UNITED STATES PATENTS 1,828,022 Brand Oct. 20, 1931 1,995,996 Moore Mar. 26, 1935 2,288,913 Moecker July 7, 1942 2,304,363 Johansen Dec. 8, 1942 2,347,321 Huber Apr. 25, 1944 2,655,041 Jacobson Oct. 13, 1953 

